Characterization of Nicotine Catabolism through a Novel Pyrrolidine Pathway in Pseudomonas sp. S-1

Shaping the future of tobacco through microbial insights: a review of advances and applications

Over the past 20 years, researchers have used multi-omics techniques to study microbial diversity and metabolic function on tobacco leaves. The unique metabolic function of tobacco microorganisms has attracted extensive attention from researchers, which is an important research field in tobacco industry to improve the intrinsic quality of tobacco leaf with microbial agents. The microorganisms are particularly rich on the surface of tobacco leaf, and their metabolic function is closely related to the change of tobacco leaf chemical composition. Some microorganisms have important metabolic functions, such as: degrading macromolecular and harmful substances in tobacco leaves, and they have different degradation rates and pathways for the substances. At present, many functions of tobacco leaf microorganisms have not been fully verified and analyzed. In the future, more novel culture methods are needed to screen and isolate microorganisms on the surface of tobacco leaves, deeply tap their metabolic potential, explore the application value of microorganisms in the tobacco industry, and further promote the innovation and development of the industry.

An update in recent research on nicotine contamination and nicotine-degrading microorganisms

Nicotine is a toxic and addictive alkaloid found in tobacco and tobacco products that is harmful to human health and is an environmental pollutant. Nicotine-degrading microorganisms are unique microorganisms with the ability to use nicotine molecules as their sole source of nitrogen and carbon needed for growth. They are capable of degrading nicotine into less toxic or non-toxic metabolites. This review describes the environment's primary nicotine contamination sources and potential hazards. It also summarizes various types of nicotine-degrading microorganisms, their optimal culture conditions, and degradation efficiency. Four different catabolic pathways of nicotine in microorganisms are discussed, and the applications of nicotine-degrading microorganisms in different fields, such as the tobacco, pharmaceutical, and environmental protection industries, are outlined. This review describes the hazards of nicotine and the current research and application of nicotine-degrading microorganisms. It provides a theoretical reference for future research on nicotine-degrading microorganisms and their applications.

Reduction of nicotine content in tobacco through microbial degradation: research progress and potential applications

Originally native to South America, tobacco and is now distributed worldwide as a major cash crop. Nicotine is the main harmful component of tobacco leaves, cigarette smoke and tobacco waste, which severely affects not only the flavor of the tobacco leaf, but also causes great damage to human health. As the anti-smoking movement continued to grow since the 1950s, and consumers become more aware of their health and environmental protection, the world tobacco industry has been committed to research, develop and produce low nicotine cigarette products with relatively low risk to human health. Among various approaches, the use of microorganisms to reduce nicotine content and improve tobacco quality has become one of the most promising methods. Due to increasing interest in nicotine-degrading microorganisms (NDMs), this article reviews recent reports on NDMs, nicotine-degrading enzymes, regulation of nicotine-degrading bacterial consortia and optimization of fermentation conditions, aiming to provide updated references for the in-depth research and application of microorganisms for the degradation of nicotine.

Analyzing the Effect of Microbial Consortia Fermentation on the Quality of HnB by Untargeted Metabolomics

Fermentation has been identified as an effective strategy to alter the chemical makeup of tobacco, thereby enhancing its quality. The deliberate introduction of microorganisms can hasten the fermentation process. In this research, microbial consortia harvested from the tobacco surface were utilized to enhance the tobacco quality. This enhancement also elevated several sensory attributes of HnB cigarettes, such as aroma richness, moisture, strength, and reduced irritation, achieving a sensory quality rating of 84.5. This marks a notable improvement compared to the 82 rating of the original, unfermented cigarettes. Untargeted metabolomics analysis revealed a decrease in total polyphenols and unsaturated fatty acids, while the levels of polyacids, alcohols, ketones, furans, and other compounds increased in the fermented tobacco. Additionally, KEGG pathway enrichment analysis indicated that the enhancement in tobacco quality through microbial consortia fermentation is linked to various biological pathways, with pathways related to fatty acid and amino acid degradation playing pivotal roles. The findings of this study will serve as a reference for the commercial production of HnB cigarettes, and the elucidated mechanism offers a theoretical basis for exploring microbial fermentation as a means to improve tobacco quality.

Characterization of cotinine degradation in a newly isolated Gram-negative strain Pseudomonas sp. JH-2

Cotinine, the primary metabolite of nicotine in the human body, is an emerging pollutant in aquatic environments. It causes environmental problems and is harmful to the health of humans and other mammals; however, the mechanisms of its biodegradation have been elucidated incompletely. In this study, a novel Gram-negative strain that could degrade and utilize cotinine as a sole carbon source was isolated from municipal wastewater samples, and its cotinine degradation characteristics and kinetics were determined. Pseudomonas sp. JH-2 was able to degrade 100 mg/L (0.56 mM) of cotinine with high efficiency within 5 days at 30 ℃, pH 7.0, and 1% NaCl. Two intermediates, 6-hydroxycotinine and 6-hydroxy-3-succinoylpyridine (HSP), were identified by high-performance liquid chromatography and liquid chromatograph mass spectrometer. The draft whole genome sequence of strain JH-2 was obtained and analyzed to determine genomic structure and function. No homologs of proteins predicted in Nocardioides sp. JQ2195 and reported in nicotine degradation Pyrrolidine pathway were found in strain JH-2, suggesting new enzymes that responsible for cotinine catabolism. These findings provide meaningful insights into the biodegradation of cotinine by Gram-negative bacteria.

Insights into Pharmacological Activities of Nicotine and 6-Hydroxy-L-nicotine, a Bacterial Nicotine Derivative: A Systematic Review

The purported cognitive benefits associated with nicotine and its metabolites in the brain are a matter of debate. In this review, the impact of the pharmacologically active metabolite of a nicotine derivative produced by bacteria named 6-hydroxy-L-nicotine (6HLN) on memory, oxidative stress, and the activity of the cholinergic system in the brain was examined. A search in the PubMed, Science Direct, Web of Science, and Google Scholar databases, limiting entries to those published between 1992 and 2023, was conducted. The search focused specifically on articles about nicotine metabolites, memory, oxidative stress, and cholinergic system activity, as well as enzymes or pathways related to nicotine degradation in bacteria. The preliminary search resulted in 696 articles, and following the application of exclusion criteria, 212 articles were deemed eligible for inclusion. This review focuses on experimental studies supporting nicotine catabolism in bacteria, and the chemical and pharmacological activities of nicotine and its metabolite 6HLN.

Bacillus sp. YC7 from intestines of Lasioderma serricorne degrades nicotine due to nicotine dehydrogenase

A large number of nicotine-containing wastes produced during the tobacco manufacturing process are seriously harmful to the environment and human health. The degradation and transformation of nicotine-containing environmental contaminants to harmless substances has become an urgent requirement. Lasioderma serricorne can grow and reproduce in nicotine-rich sources, and their intestinal microbiota show promising potential to degrade and utilize nicotine. The purpose of this study is to screen and identify nicotine-degrading bacteria from the intestines of L. serricorne and explore their degradation characteristics. A dominant strain, YC7, with significant nicotine degradation capabilities was isolated from the intestines of L. serricorne. The strain was identified as Bacillus using a polyphasic approach. The test results showed it can produce multiple enzymes that include β-glucosidase, cellulase, proteases, and amylases. The nicotine-degrading bacteria were functionally annotated using databases. Nicotine dehydrogenase (NDH) was found by combining an activity tracking test and protein mass spectrometry analysis. The YC-7 NDH in the pathway was molecularly docked and functionally verified via the gene knockdown method. The binding ability of nicotine to nicotine-degrading enzymes was investigated using molecular docking. A high-efficiency nicotine-degrading bacteria, YC-7, was isolated and screened from tobacco, and the gene functions related to degradation were verified. This investigation provides a new hypothesis for screening nicotine-degrading bacteria and increases our knowledge of potential nicotine-degrading microbial sources.

Nicotine metabolism pathway in bacteria: mechanism, modification, and application

Nicotine is a harmful pollutant mainly from the waste of tobacco factories. It is necessary to remove nicotine via high efficient strategies such as bioremediation. So far, an increasing number of nicotine degrading strains have been isolated. However, their degrading efficiency and tolerance to high content nicotine is still not high enough for application in real environment. Thus, the modification of nicotine metabolism pathway is obligated and requires comprehensive molecular insights into whole cell metabolism of nicotine degrading strains. Obviously, the development of multi-omics technology has accelerated the mechanism study on microbial degradation of nicotine and supplied more novel strategy of strains modification. So far, three pathways of nicotine degradation, pyridine pathway, pyrrolidine pathway, and the variant of pyridine and pyrrolidine pathway (VPP pathway), have been clearly identified in bacteria. Muti-omics analysis further revealed specific genome architecture, regulation mechanism, and specific genes or enzymes of three pathways, in different strains. Especially, muti-omics analysis revealed that functional modules coexisted in different genome loci and played additional roles on enhanced degradation efficiency in bacteria. Based on the above discovery, genomic editing strategy becomes more feasible to greatly improve bacterial degrading efficiency of nicotine.

Expression and functional identification of two homologous nicotine dehydrogenases, NicA2 and Nox, from Pseudomonas sp. JY-Q

Nicotine contamination in tobacco waste effluent (TWE) from tobacco industry is a serious threat to public health and environment. Microbial degradation is an impending approach to remove nicotine and transform it into some other high value chemicals. Pseudomonas sp. JY-Q exhibits high efficiency of degradation, which can degrade 5 g/L of nicotine within 24 h. In strain JY-Q, we found the co-occurrence of two homologous key enzymes NicA2 and Nox, which catalyze nicotine to N-methylmyosmine, and then to pseudooxylnicotine via simultaneous hydrolysis. In this study, recombinant NicA2 and Nox were expressed in E. coli BL21(DE3) and purified. In vitro, the activity of recombinant NicA2 and Nox was accelerated by adding co-factor NAD⁺, suggesting that they worked as dehydrogenases. The optimal reaction conditions, substrate affinity, catabolism efficiency, pH-stability and thermal-stability were determined. Nox showed lower efficiency, but at a higher stability level than NicA2. Nox exhibited wider pH range and higher temperature as optimal conditions for the enzymatic reaction. In addition, The Nox showed higher thermo-stability and acid-stability than that of NicA2. The study on enzymatic reaction kinetics showed that Nox had a lower Km and higher substrate affinity than NicA2. These results suggest that Nox plays more significant role than NicA2 in nicotine degradation in TWE, which usually is processed at low pH (4-5) and high temperature (above 40 °C). Genetic engineering is required to enhance the affinity and suitability of NicA2 for an increased additive effect on homologous NicA2 and Nox in strain JY-Q.

Availability of nutrients, removal of nicotine, heavy metals and pathogens in compounds obtained from smuggled cigarette tobacco compost associated with industrial sewage sludge

This study evaluated the chemical and microbiological properties of the compost obtained from the tobacco of smuggled cigarettes (SCT) and industrial sewage sludge (ISS). The composting was carried out in three reactors from different combinations of residues. The compost was analyzed to verify the percentage of nicotine removal, heavy metals, nutrient content and the inactivation of pathogenic microorganisms. The concentration of heavy metals: Ni, Cd, Cr, Pb, Cu, Zn, Fe and Mn in the composts obtained from the three reactors was below the values set for their use in soils. The NPK content ranged between 8.31% and 12.43%, indicating that the compost produced can add nutritional benefits to the plants. The nicotine removal, 72.6% (R1), 96.4% (R2) and 99.6% (R3) indicated efficiency of the composting process in reactors in the degradation of this substance. The results of pathogenic microorganism analysis showed that the three composts obtained from reactors R1, R2 and R3 met the sanitation standards for agricultural use according to the normative of maximum limits of contaminants allowed in organic compounds. These results show that the treatment of SCT and ISS by the process of composting in reactors may be an ecologically viable alternative.

Kinetics and Catabolic Pathways of the Insecticide Chlorpyrifos, Annotation of the Degradation Genes, and Characterization of Enzymes TcpA and Fre in Cupriavidus nantongensis X1T

Chlorpyrifos is one of the most used organophosphorus insecticides. It is commonly degraded to 3,5,6-trichloro-2-pyridinol (TCP), which is water-soluble and toxic. Bacteria can degrade chlorpyrifos and TCP, but the biodegradation mechanism has not been well-characterized. Recently isolated Cupriavidus nantongensis X1^T can completely degrade 100 mg/L chlorpyrifos and 20 mg/L TCP with half-lives of 6 and 8 h, respectively. We annotated a complete gene cluster responsible for TCP degradation in recently sequenced strain X1^T. Two key genes, tcpA and fre, were cloned from X1^T and transferred and expressed in Escherichia coli BL21(DE3). Degradation of TCP by X1^T whole cell was compared with that by the enzymes 2,4,6-trichlorophenol monooxygenase and NAD(P)H:flavin reductase expressed and purified from E. coli BL21(DE3). Novel metabolites of TCP were isolated and characterized, indicating stepwise dechlorination of TCP, which was confirmed by TCP disappearance, mass balance, and detection and formation kinetics of chloride ion from TCP.

Degradation of Phenylurea Herbicides by a Novel Bacterial Consortium Containing Synergistically Catabolic Species and Functionally Complementary Hydrolases

Phenylurea herbicides (PHs) are frequently detected as major water contaminants in areas where there is extensive use. In this study, Diaphorobacter sp. strain LR2014-1, which initially hydrolyzes linuron to 3,4-dichloroanaline, and Achromobacter sp. strain ANB-1, which further mineralizes the produced aniline derivatives, were isolated from a linuron-mineralizing consortium despite being present at low abundance in the community. The synergistic catabolism of linuron by the consortium containing these two strains resulted in more efficient catabolism of linuron and growth of both strains. Strain LR2014-1 harbors two evolutionary divergent hydrolases from the amidohydrolase superfamily Phh and the amidase superfamily TccA2, which functioned complementarily in the hydrolysis of various types of PHs, including linuron ( N-methoxy- N-methyl-substituted), diuron, chlorotoluron, fluomethuron ( N, N-dimethyl-substituted), and siduron. These findings show that a bacterial consortium can contain catabolically synergistic species for PH mineralization, and one strain could harbor functionally complementary hydrolases for a broadened substrate range.